Controlled ingition discharge tube system



June 1, 1943. J. w. DAWSON 2,320,916

CONTROLLED IGNITION DISCHARGE TUBE SYSTEM Filed June 19, 1942 arCZw,%.

PatcntedJune' l, 1943 couraounp rcnmox mscmmcn 'runa srsmrr John W.Dawson, West Newton, Mala, assignor to Raytheon Manufacturing Company,Newton,

Mass a corporation of Delaware Application June 19, 1942, Serial No.447,654

11 Claims. (Cl. 171-91) This invention relates, to controlled ignitiondischarge tube systems, and particularly to firing arrangements for suchtubes. The tubes referred to hereinabove are of. the type having a. D001cathode and an igniting electrode which is adapted when supplied with anigniting impulse to initiate an are on said pool;

An object of the present invention is the provision of a system forreliably firing controlled ignition discharge tubes.

Another object of the present invention is the provision of means, incontrolled ignition discharge systems having a circuit in which the rateof current flow is varying, for firing a controlled ignition dischargetube when the rate of current flow in said circuit has reached apredetermined value.

Still another object of the present invention is the provision, in acontrolled ignition discharge tube system in which the anode voltageapplied to said tube is varying, of means for supplying ignitingimpulses to the igniting electrode of said tube when the anode voltagethereon has reached a predetermined value.

In certain condenser discharge systems in which the condenser isdischarged through an inductance the discharge tends to be oscillatoryand the potentials across said condenser and said inductance reverse inpolarity." In certain of such systems it is desired to fire a controlledignition discharge tube upon such reversal of potential. The tube to befired, for example may be a shunt tube arranged across the inductance toenable the exponential decay of the current flowing through saidinductance. Therefore, a further object of the present invention is theprovision in a system of the type described of means for firing thecontrolled ignition discharge tube when the reversed potential on thecondenser, a /or the inductance has reached a predetermined value, andfor delaying said firing until said value has been reached.

A still further object of the present invention is the provision of acondenser discharge system of the type hereinbefore described in whichigniting impulses are supplied to the shunt tube when the reversedpotential thereon has reached a high enough value to insure reliableignition of 7 the figure is a schematic ram of a condenser weldingsystem utilizing c rolled ignition discharge tubes.

Referring now to the figure, a welding load I is to be supplied withwelding current from the.

secondary 2 of a welding transformer '3 having a primary winding 4. Theprimary 4 is adapted to be s pplied with energy from the discharge of acondenser 5. Condenser 5 is adapted to be charged from any suitablesource of direct current, such as for example, a direct currentgenerator, battery, rectifier, or the like. For this purpose saidcondenser may have its negative side connectedto a terminal 6, and itspositive side connected to a terminal 1, terminals 6 and I being adaptedto be connected to a suitable source of direct current supply. Condenser5 may have its positive side connected directly to one end of theprimary winding 4, and its negative side connected through a controlledignition discharge tube 8 to theother side of the primary winding 4.Tube. 8 is preferably of the type having a pool cathode and anelectrostatic igniting electrode. By the term electrostatic ignitingelectrode, I

refer to the type of igniting electrode insulated and separated from thepool by a thin glass c overing. Tube 8 has its anode 9 connected to oneend of the primary winding 4, and it's cathode I ll connected to thenegative side of condenser 5. Igniting impulses may be supplied to theigniting electrode ii of tube 8 through the secondary winding I! of anigniting transformer l3 having a primary winding i4. Any suitable meansmay be used to supply pulses of current to the primary winding l4, theone here-illustrated consisting of a condenser l5 adapted to be chargedfrom any suitable source of direct current [6 through a current lmitingresistance ll. Condenser I5 is connected to the primary winding ll ofthe igniting transformer l3 through a manually operable switch l8,wh1chswitch is adapted upon being closed to discharge condenser [5 throughthe primary winding I 4. A resistance l9 may be arranged across theprimarywinding II.

It will be seen that when switch i8 is closed an igniting impulse is'supplied to the igniting electrode ll of tube 8, and tube 8 is therebyfired. Upon the firing of tube 8, condenser 5 discharges through theprimary winding 4 of the welding transforme 3. As condenser [discharges,the voltage across inductance 4 decreases as the current passingtherethrough increases, the voltage reaching a zero value when thecurrent flow is at 2 a maximum. Due to the inductance associated withsaid circuit, current continues to fiow in the original directionthrough the primary winding .4 as the potential across said winding 4reverses.-

. In order to enable the current flowing through said'winding to decayexponentially another controlled ignition discharge tube 23 is arrangedin shunt across the primary winding 4. lube 23 may be similar to tube 3,and may be provided with a pool type cathode 2| connected to one endof-the primary winding 4 and 'ananode 22 con-' nected to theend of theprimary winding 4 which is connected to anode 3 of tube 3. Tube 23 maybe provided with an igniting electrode 23 of the same type as ignitingelectrode llof tube 3. Igniting impulses fo firing tube 23 may besupplied to the igniting electrode 23 from the secondary winding 24 of,an igniting transformer 25 having a primary winding 23 which is adaptedto" be connected to. a suitable source of igniting impulses.

When condenser 3 is discharged into the pri- -mary winding 4 of thewelding transformer 3 upon firing of tube 3, the potential drop acrossand to thereby enable the exponential decay of a' fairly steady valueand there will be insufllcient change in the flux in said transformer toinduce an igniting pulse in the secondary 24 thereof. It is accordinglydesired that tube 23 shall not conduct until the voltage applied to theanode 22 of tube 23 by the reversed potential across the primary winding4 has reached a value sumcient to cause tube 23 to conduct when anigniting impulse is applied to the igniting electrode thereof.

This may be accomplished by applying a cut-off bias to the grid 33 oftube 23 until such time as tube 23 is ready to conduct. For this purposea condenser 32, in series with the resistance 33 of a potentiometer 34and in series with anotherresistance 35, is arranged across condenser 3.

When condenser 3 is charged condenser 32 is charged in the samedirection. In order that a constant voltage may be applied acrosscondenser 32 so as .to limit the potential-to which said condenser ischarged to a constant value, a constant voltage device, such as forexample. a glow discharge tube 33, has one side thereof connected to thepositive side of condenser 32 and the other side thereof connected to apoint intermediate resistance 35 and potentiometer 34.. The arm 31 ofpotentiometer 34 is connected through a suitable grid resistor 33 to thegrid 33 of tube 23.

It will be seen that when condenser E is being charged, condenser 32will be charged to the voltage determined by the glow discharge tube 33.

The direction of the charge on condenser 32 is such that a negativevoltagewill be applied tothegrid 33 of tube 23 by said condenser,thereby the current through primary winding 4. The reversed potentialacross condenser 5 may be used to provide the igniting impulses for theprimary winding 23. For this purpose the primary winding 23 has one endthereof connected to the side of condenser 3 which was originallycharged to a negative potential. The other side of the primary winding26 is connected in series with a resistor 21 and a controlled gaseousrectifying tube 23 to the positive side of condenser 3. Tube 23 ispreferably of the type having a continuously energized cathode 23 and acontrol grid 33.

preventing conduction in said tube. As condenser 5' is discharged thepotential across condenser 5 reverses.

As condenser 5 is discharging condenser 32 also tends todischarge, butdue to the impedances in series with condenser 32 the discharge of saidcondenser is comparatively very much lower.

Condenser 5 is discharged and the potential thereacross reverses andbuilds up before condenser 32 has discharged to any appreciable extent.Therefore, it will be seen that when the potential across condenserSreverses. tube 23 will not conduct due to the bias applied thereto bycondenser 32. It

' will be seen that when the potential across con- Anode 3| of tube 23is connected to oneend of V resistor 21, while the cathode 23 of saidtube is connected to the positive side of condenser 3. It will be seenthat when the potential across condenser 3 reverses, a positivepotential is applied to the anode 3| of tube 23, and tube 23 willthereupon conduct. Upon conduction of tube 23 a pulse of current willpass through the primary 23 of igniting transformer 25. It will furtherbeseen that upon reversal of the potential across primary winding 4 apositive potential will be applied to the anode 22 of tube 23. Thispotential will rise as the'reversal of potential across the winding 4continues until it reaches a value at which tube 23 is ready to conductand at which value tube 23 will conduct if igniting impulses aresupplied thereto.

Referring back to tube 23, it will be seenthat tube 23 tends to conductimmediately upon the reversalof potential, and the igniting impulsesproduced by the initial conduction of tube-23 may be,ap-

- plied to the igniting electrode 23 of tube 23 before the reversedpotential applied to the anode 22 of tube 23' has reached a suflicientvalue to cause tube 23 to fires In such event, tube 23 will not befired, for even though tube 23 continues to conduct, the current passingthrough' said tube and through the primary winding 23 of the ignitingtransformer "will then have reached denser -5 reverses, said potentialis applied through resistance 35 and through a portion of thepotentiometer resistance 34 to grid 33. The direction of this potentialis such as to tend to make tube 23 conduct, that is condenser 5 tends toapply. a positive voltage to the grid 33 of tube 23 when the potentialon said condenser is reversed. Tube 23-will only begin to conduct when.the reversed potential across condenser 3 reaches such a value that thepotential applied 'by said condenser to the grid 33 of tube 23 overcomesthe cut-on bias applied to said grid by condenser 32. The potentialapplied to grid 33 by condenser 3 is equal to the potential across saidcondenser less the voltage drop across resistance 35, a

portion of resistance 33 of potentiometer 34, and a small amount acrossgrid resistor 33. The potentiometer applied by a condenser 32 to grid 33is equal to the potential across said condenser minus the potential dropacross the portion of resistance 33 of potentiometer 34 which is to theleft of the potentiometer arm 31, and'resistance v 33. It will be seenthat by varying these resistances the proportion of the potentials oneither of condensers 5- or 32 which is applied to the grid 33 of tube 23can be likewise varied. 7 It will be apparent that by adiustingpotentiometer arm 81 the precise point at which tube 28 will begin toconduct can be determined. 7

A condenser 88 may be arranged between the grid 80 of the cathode 28 oftube 28 to eliminate transients. In order to enable tube 28 to startconducting rapidly as soon as the cut-oil bias on its grid iseliminated, a condenser 48 may be arranged in shunt across resistor 21,the condenser lowering the impedance of the circuit to a surge ofcurrent. In such case, resistance 21 acts as a bleeder. Condenser 48also serves to prevent damage to tube 28 in case tube 28 fails to firewhen the potential across condenser 8 reverses, since the condenser 48becomes charged in a direction to oppose the flow of too much currentthrough the circuit including tube 28. A resistance 4| may be arrangedacross the primary. winding 28 of the igniting transformer 25.

In one specific system employing my invention, the following constantsare used for certain elements of the system. Glow discharge" tube 86 hasa constant voltage drop of volts. Condenser 28 has a value of .6microfarad. Resistance 85 plus the portion of resistance 88 to the rightof potentiometer arm 81 has'a total value of .6 megohm. The portion ofresistance 83 between the potentiometer arm 81 and the negative side ofcondenser 82 has a value of .4 megohm. It will be seen that whencondenser 5 of this system is charged, condenser 82 is charged to avalue of 60 volts, and that this 60 volts is applied through gridresistor 88 to the grid 88 of 'tube 28 thereby preventing said tube fromconducting. In this specific system tube 28 is of the type requiringabout volts anode voltage to enable said tube to conduct, and it ispreferred to have said tube conduct when the anode voltage thereon is100 volts. As will be apparent from the following, the parameters of thecircuit are such that an igniting impulse is applied to the ignitingelectrode 28 of tube 20 only when the anode voltage on tube 20 hasreached 100 volts. This is accompl shed as is explained below bypreventing tube 28 from conducting until the anode voltage on tube 28 isof this value.

Condenser 5 which is originally charged to from 1500 to 3000 volts,depending upon the welding load, is discharged by' the firing of seriestube 8 into the primary winding 4 of transformer 8. The voltageacrossprimary winding 4 declines to zero and then reverses. Tube 28 doesnot fire immediately upon the reversal of such potential even though apositive voltage is applied to the anode 8| thereof. This is due to thebiasapplied by condenser 82 whichis 60 volts. Tube 28 cannot fire untilthe bias applied by condenser 82 is overcome. Tube 28 in this system isof the type which is adapted to conduct when the bias on its grid 88 issubstantially zero or positive. The bias applied to said grid becomeszero when the reversed potential of condenser 5 minus the drop acrossresistance 88 and the portion of resistance 34 to the right ofpotentiometer arm 81 is equal to the potential of condenser 82 minus thepotential drop across the portion of resistance 88 to the left of thepotentiometer arm 81. Assuming that the reversed potential across the aprimary winding 4 has reached a value of 100 volts, and that thepotential drop in tube 8 is 10 volts, it will be seen that the reversedpotential on condenser 5 is 90 volts. When the potential on condenser 5minus the potential drop across resistance 85 and the portion ofresistance 84 to the right of potentiometer arm 81 is equal to thepotential across condenser 82 minus the potential drop across the sideof resistance 88 to the left of potentiometer arm 81 Rl/R2=El/E2 whereRi=1the value of the portion of the resistance 82 to the left ofpotentiometer arm 81 which as stated hereinabove was equal to .4 megohm.

Rz=the value of resistance 35 plus the value of the portion of theresistance 88 to the right of potentiometer arm 81, which as statedhercinbefore was equal to .6 megohm.

El=potential across condenser 82 which is 60 volts.

E==reversed potential acrosscondenser 8 which is 90 volts.

Applying these figures to the equation Thus, it will be seen that whenthe reversed potential across the primary winding 4 is volts, thepotential across condenser 8 then being 90 volts, the potential acrosscondenser 5 nullifies the efiect on the grid 88 of the potential acrosscondenser 82 thereby removing the cut-oi! bias applied by said condenser82 and thereby enabling'tube 28 to conduct.

Upon conduction of tube 28 an igniting impulse is applied to theigniting electrode 28 to tube 28, and since the anode voltage on tube 20has reached the predetermined value of 100 volts at which tube 20 iscapable of being fired, tube 20 is thereupon ignited.

From the foregoing it will be seen that the precise point at which tube28 is to be fired may be determined by proportioning the resistances R1and R2. This, of course, can be readily accomplished in the systemillustrated, by adjusting potentiometer arm 81. Another way ofdetermining the precise firing point is by changing the potential towhich condenser 82 is charged.

This also may be done by simply inserting a resistance in series withglow discharge tube 86,

or by utilizing a glow discharge tube having a difierent constantvoltage drop.

From the foregoing description it will be seen that I have providedmeans for reliably firing a controlled ignition discharge tube at apredetermined point when the anode voltage applied to said tube isvarying. It will also be seen that I have disclosed means for-firing acontrolled ignition discharge tube at a precise point in relation to acircuit in which the current is varying. It will furthermore be seenthat I have provided means for firing a controlled ignition dischargetube at a precise point during the discharge of a condenser through aninductance, and specifically have shown means for precisely firing theshunt tube arranged across the inductance.

While I have pointed out hereinabove certain modifications that may bemade in the system here described, it will be apparent that othermodifications may be made in acco dance with the teaching of thisinvention. Therefore it is desired that the appended claims be given abroad interpretation commensurate with the scope of the invention withinthe art.

What is claimed is:

1. In an ele'ctrical system including an electrical energy storagedevice across which the potential is first of one polarity andthereafter 4. declines and builds up with a reverse polarity, acontrolled ignition discharge tube adapted to be fired when the reversedpotential across said I device has reached a predetermined value, meansfor supplying igniting impulses to said tube, and means for deenergizingsaid igniting impulses supplying means, said deenergizing means beinadapted to be rendered ineffectual when said reversed potential hasreached a predetermined value.

2. A condenser discharge system having a condenser adapted to bedischarged through a load containing inductance, said dischargetending'to be oscillatory and the polarity of the potential across saidinductance reversing, a controlled ignition discharge tube arranged inshunt across said load and adapted to be fired when said reversedpotential has reached a predetermined value, means for supplyingigniting impulses to said tube, and means for deenergizing said ignitingimpulses supplying means, said -deenergiz-' ing means being adapted tobe rendered ineffectual when said reversed potential has reached apredetermined value.

3. In an electrical system having two points therein across which thepotential is first of one polarity and'thereafter declines and builds upwith a reverse polarity, a controlled ignition discharge tube adapted tobe fired when the reversed potential across said two points has reacheda predetermined value, means for supplying igniting impulses to saidtube, and means for deen- 'ergizing said igniting impulses supplyingmeans,

' clines and builds up with a reverse polarity, a

controlled ignition discharge tube adapted to be fired when the reversedpotential across said device has reached a predetermined value, meansfor supplying igniting impulses for firing said ignition tube, saidmeans including a rectifyin tube adapted to conduct upon reversal of thepotential across said device to thereby supply igniting impulses,and-means for preventing conduction of said rectifying tube until thereversed potential on said. electrical energy storage device has reacheda predetermined value.

5. In I an electrical system including a condenser across which thepotential is' first of one polarity and thereafter declines and buildsup with a reverse polarity, a controlled ignition discharge tube adaptedto be fired when the reversed potential across said condenser hasreached a predetermined value, means for supplying igniting impulses forfiring said ignition tube, said means including a rectifying tubeadapted to con- 4 duct upon reversal of the potential across saidcondenser to thereby supply igniting impulses, and means for preventingconduction of said rectifying tube until the reversed potential on saidcondenser has reached a predetermined value.

6. In an electrical systemincluding an induct ance across which thepotential is first of one polarity and thereafter declines and builds upwith a reverse polarity, a controlled ignition discharge tube adapted tobe fired when the reversed potential across 'said' inductance hasreached a predetermined value, means for supplying for firing saidignition tube, said means including a rectifying tube adapted to conductupon reversal of the'potential -across said inductance, and means for weventing conduction ofsaid rectifying tube until the reversed potentialon said inductance has reached a predetermined value.

I. In an electrical system having two points therein across which thepotential is first of one polarity and thereafter declinesand builds upwith a reverse polarity, a controlled ignition discharge tube adapted tobe fired when the retential is first of one polarity and thereafterdeclines and builds upwith a reverse polarity, a controlled ignitiondischarge tube adapted to be fired when the reversed potential acrosssaid device has reached a predetermined value, means for supplyingigniting impulses for firing said ignition tube, said means including arectifying tube having a control grid, said rectifying'tube being,adapted to conduct upon reversal of the potential across said device tothereby supply lgniting impulses; and electrical energy storage meansarranged so that at least a part of the potential thereon is impressedon said grid to prevent conduction of said rectifying tube, said devicebeing connected so that at least a part of the reversed potentialthereon is applied to said grid with a polarity to oppose the potentialapplied thereto by said electrical energy storage means. saidldevicebeing'adapted, when said reversed potential has reached a predeterminedvalue, to enable said rectifying tube to conduct.

9. In an electrical system including an elec-' trical energy storagedevice across which the po-' tential is first of one polarityandthereafter declines and builds up with a reverse polarity, a controlledignition discharge tube adapted to be fired when the reversed potentialacross said de vice has reached a predetermined value, means forsupplying igniting impulses for firing said ignition tube, said meansincluding a rectifying tube having a control grid, said rectifying tubebeing adapted to conduct upon reversal of the A potential across saiddevice to thereby supply igniting impulses, and a condenser adapted tobe charged to a predetermined potential by the po-. tential across saiddevice, said condenser being arranged so that at least a part of thepotential thereon is impressed on said grid to prevent OOH? duction ofsaid rectifying tube, said device being connected so that at least apart of the reversed potential thereon is applied to said grid with .a'

polarity to oppose the potential applied thereto by said condenser, saiddevice being adapted,

enable said rectifying tube trol grid, said rectifying tube beingadapted to conduct upon reversal of the potential across said condenserto thereby supply igniting impulses, and a second condenser, adapted tobe charged to a predetermined potential by the potential across saidcondenser, said second condenser being arranged so that at least a partof the potential thereon is impressed on said grid to prevent conductionof said rectifying tube, said first-mentioned condenser being connectedso that at least a part 01' the reversed potential thereon is applied tosaid grid with a polarity to oppose the potential applied thereto bysaid second condenser, said first-mentioned condenser being adapted,when said reversed potential has reached a predetermined value, to causesaid rectifying tube to conduct.

' 11. A condenser discharge system having a. condenser adapted to becharged and to be thereafter discharged through a load containinginductance, said discharge tending to be oscillatory and the polarityoi. the potential across said load reversing, a controlled ignitiondischarge tube voltage, the voltage on said second condenser arranged inshunt across said load and adapted to be fired when said reversedpotential has reached a predeterminedvalue, means for supplying ignitingimpulses to said tube, said means including a controlled rectifying tubeadapted upon conduction thereof to supply said ignitingimpulses, saidrectifying tube having a control grid, and a second condenser adapted tobe charged with. the same polarity as said flrstmentioned condenser,means for limiting the charge on said second condenser to apredetermined being applied to said control grid with a polarity toprevent conduction thereof, said first-mentioned condenser beingconnected to said control grid and being adapted-when the potential onsaid first-mentioned condenser has reversed to app y a potential to saidcontrol grid with a polarity opposed to that of the voltage applied bysaid second condenser to thereby enable said rectifying tube to conductwhen said reversed potential has reached a predetermined value.

JOHN W. DAWSON.

CERTIFICATE OF CORRECTION. Patent No. 2,520,916. I June 1, 191g.

JOHN w. mwson.

It is hereby certified that error appears in the printed specification.

of the above numbered patent requiring correction as follows: Page 2,eec- 0nd column, line 65-66, for "potentiometer" read potential; line66, strike out "a" before "condenser"; page 11., second column, line 15,claim 7, after "and'[ insert --me.e.ns.--; and that the said LettersPatent should be read with this correction therein thgt the same mayconform to the record of the case in the Patent Office.

v Signed and sealed this 20th day of July, A. D. 19h5.

Henry Van Aredale, (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION. Patent 11 2,520,916. d June 1, 194.5.

' JOHN w. DAWSON. v

- It is hereby certified that error appears in the printedspecification.

of the'above numbered patent requiring correction as fo1 1ows: iage 2,sec-' 0nd column, line -6566, for "potentiometer" read "potentialline66, strike out "a" before "condenser"; page 14., second column, line 15,claim 7, after "and" insert --me.ans and that tlge said Letters Patentshould be read with this correction therein thgt the same may confdrmwto the record of the case in the Patent Office.

. Signed and sealed this 20th day of July, A.) D. 1915.

Henry Van Arsdale, (Seal) Acting C onnni'ssioner of Patents.-

